1. Field of the Invention
The present invention relates to a jet-propulsion watercraft which ejects water rearward and planes on a water surface as the resulting reaction. More particularly, the present invention relates to a jet-propulsion watercraft that can maintain steering capability even when the throttle is operated in the closed position and propulsion force is thereby reduced.
2. Description of the Related Art
In recent years, so-called jet-propulsion personal watercraft (PWC) have been widely used in leisure, sport, rescue activities, and the like. The personal watercraft is configured to have a water jet pump that pressurizes and accelerates water sucked from a water intake generally provided on a bottom of a hull and ejects it rearward from an outlet port. Thereby, the personal watercraft is propelled.
In the personal watercraft, in association with a steering handle of a general bar type, a steering nozzle provided behind the outlet port of the water jet pump is swung either to the right or left, to change the ejecting direction of the water to the right or to the left, thereby turning the watercraft.
A deflector is retractably provided behind the steering nozzle for blocking the water ejected from the steering nozzle. The deflector is moved downward to deflect the ejected water forward, and as the resulting reaction, the personal watercraft moves rearward. In some watercraft, in order to move rearward, a water flow is formed so as to flow from an opening provided laterally of the deflector along a transom board to reduce the water pressure in an area behind the watercraft.
In the above-described personal watercraft, when the throttle is moved to a substantially fully closed position and the water ejected from the water jet pump is thereby reduced, during forward movement and rearward movement, the propulsion force necessary for turning the watercraft is correspondingly reduced, and the steering capability of the watercraft is therefore reduced until the throttle is re-opened.
To solve the above-described condition with a mechanical structure, the applicant disclosed a jet-propulsion personal watercraft comprising a steering component for an auxiliary steering system which operates in association with the steering handle in addition to a steering nozzle for the main steering system in Japanese Patent Application No. Hei. 2000-6708.
Also, for the purpose of achieving a lightweight watercraft, the applicant disclosed a jet-propulsion personal watercraft in Japanese Patent Application No. Hei. 2000-173232, in which a sensor is adapted to detect a throttle-close operation, a steering operation, or the like, and an engine speed is increased according to the detection.
The present invention addresses the above-described condition, and an object of the present invention is to provide a jet-propulsion watercraft, which can maintain steering capability according to the cruising speed thereof even while an operation which closes the throttle is performed and the amount of water ejected from a water jet pump is thereby reduced. More specifically, the watercraft is adapted to execute a control for increasing the engine speed while the throttle-close operation and the steering handle operation are detected. The engine speed increase is controlled so that the rate of change upon the control is subdued making the watercraft continue to turn smoothly.
According to the present invention, there is provided a jet-propulsion watercraft comprising: a water jet pump that pressurizes and accelerates sucked water and ejects the water from an outlet port provided behind the water jet pump to propel the watercraft as a reaction of the ejecting water; an engine for driving the water jet pump; a steering operation means that operates in association with a steering nozzle of the water jet pump; a steering position sensor for detecting a predetermined steering position of the steering operation means; a throttle-close operation sensor for detecting a throttle-close operation; a cruising speed obtaining means for obtaining a cruising speed of the watercraft; and an electric control unit, wherein the electric control unit is adapted to increase the engine speed to a predetermined engine speed during the detection of the predetermined steering position by the steering position sensor and the detection of the throttle-close operation by the throttle-close operation sensor while changing an increasing speed of the engine speed according to the cruising speed obtained by the cruising speed obtaining means.
According to the jet-propulsion watercraft of the present invention, the engine speed is increased to the predetermined engine speed while the watercraft is steered, this operation is detected by the steering position sensor, and while the throttle-close operation is detected by the throttle-close operation sensor. Therefore, the water sufficient to turn the watercraft is ejected from the water jet pump, and the steering capability can be maintained even while the throttle-close operation is performed. Also, since the increasing speed of the engine speed is changed according to the cruising speed obtained by the cruising speed obtaining means, the ejected water amount adapted to the cruising speed can be obtained, and the rider is given improved steering feeling.
Herein, control for increasing the engine speed is referred to as xe2x80x9csteering assist mode controlxe2x80x9d, and the xe2x80x9cthrottle-close operationxe2x80x9d means that operation is performed to bring the throttle toward a closed position by a predetermined amount or more.
It should be noted that the throttle-close operation sensor of the present invention is not limited to the engine speed sensor and the throttle position sensor. For example, it is possible to use a sensor placed in a system connecting a throttle lever and a throttle valve for detecting an operation of the system while the throttle-close operation is performed. Also, it is possible to use a sensor for detecting an air-intake pressure and an air-intake amount of the engine.
Under the steering assist mode control, the engine speed can be increased by changing at least any of the fuel injection timing of the fuel injection system of the engine, the ignition timing of an ignition system of the engine, and the fuel injection amount of the fuel injection system of the engine. In this case, the engine speed can be increased without actual operation of the throttle.
In the jet-propulsion watercraft, the speed for increasing the engine speed to the predetermined engine speed according to the change in the cruising speed may be changed stepwise.
It is preferable that in the jet-propulsion watercraft, smaller increasing speeds of the engine speed are set for higher cruising speeds. Thereby, the change in the cruising speed occurring in transition to the steering assist mode control can be subdued, and the steering feeling under the control is improved.
In the jet-propulsion watercraft, a cruising speed sensor for detecting the cruising speed of the watercraft may be used as the cruising speed obtaining means. Also, the cruising speed may be calculated from the engine speed.
The jet-propulsion watercraft may further comprise: an increasing speed table that prestores an increasing speed of the engine speed according to the cruising speed. The increasing speed according to the cruising speed obtained by the cruising speed obtaining means may be read from the increasing speed table and the engine speed may be increased to the predetermined engine speed based on the increasing speed read from the increasing speed table. Thereby, the control for changing the increasing speed of the engine speed can be more simply executed. To obtain the stored increasing speeds of the engine speed that give preferable steering feeling, the engine speeds associated with a variety of actual cruising speeds are experimentally increased to the predetermined engine speed.
The increasing speed table may be adapted to divide a predetermined cruising speed range into a plurality of speed ranges and set smaller increasing speeds of the engine speeds for higher speed ranges.
More specifically, the increasing speed table may be adapted to divide a predetermined cruising speed range into first, second, and third speed ranges which are set in the order from low to high, and store smaller increasing speeds set for higher speed ranges. In this case, when the obtained cruising speed is in the first speed range, the engine speed is increased to the predetermined engine speed based on the first increasing speed. When the obtained cruising speed is in the second speed range, the engine speed is increased based on a second increasing speed smaller than the first increasing speed, and in the middle thereof, when the cruising speed decreases to the first speed range, the increasing speed is switched from the second increasing speed to the first increasing speed and in time, the engine speed reaches the predetermined engine speed. Likewise, when the cruising speed is in the third speed range, the engine speed is increased based on a third increasing speed smaller than the second increasing speed, and in the middle thereof, when the cruising speed decreases to the second speed range, the increasing speed is switched from the third increasing speed to the second increasing speed. Then, when the cruising speed further decreases to the first speed range, the increasing speed is switched from the second increasing speed to the first increasing speed, and in time, the engine speed reaches the predetermined engine speed.
According to the present invention, there is also provided a jet-propulsion watercraft comprising: a water jet pump that pressurizes and accelerates sucked water and ejects the water from an outlet port provided behind the water jet pump to propel the watercraft as a reaction of the ejecting water; an engine for driving the water jet pump; a steering operation means that operates in association with a steering nozzle of the water jet pump; a steering position sensor for detecting a predetermined steering position of the steering operation means; a throttle-close operation sensor for detecting a throttle-close operation; an obtaining means for obtaining one of a cruising speed of the watercraft and torque of the engine; and an electric control unit, wherein the electric control unit is adapted to increase the engine speed during the detection of the predetermined steering position by the steering position sensor and the detection of the throttle-close operation by the throttle-close operation sensor so that the value obtained by the obtaining means becomes a predetermined target value while changing an increasing speed of the engine speed based on a difference value between a value obtained by the obtaining means and the target value.
According to the jet-propulsion watercraft, the engine speed is increased so that the value obtained by the obtaining means becomes the target value while the steering operation means is operated, this operation is detected by the steering position sensor, and while the throttle-close operation is detected by the throttle-close operation sensor. Therefore, the water sufficient to turn the watercraft is ejected from the water jet pump, and the steering capability can be maintained even while the throttle-close operation is performed. Also, since the increasing speed of the engine speed is changed according to the difference value between the value obtained by the obtaining means and the corresponding target value, the ejected water amount adapted to the actual cruising speed or the engine torque in substitution for the cruising speed can be obtained, and the rider is given improved steering feeling.
It is preferable that in the jet-propulsion watercraft, the smaller increasing speeds of the engine speed are set for larger difference values. Thereby, the change in the cruising speed in transition to the steering assist mode control can be subdued, and the steering feeling under the control is improved.
It is preferable that the increasing speed of the engine speed is set smaller than usual when the difference value is larger than a predetermined value. In this case, two different increasing speeds may be provided. The larger increasing speed is used when the difference value is not larger than the predetermined value for, for example, a normal mode. On the other hand, the smaller increasing speed is used when the difference value is larger than the predetermined value for an extended mode which extends the time required for increasing the engine speed up to the predetermined target value from usual control condition, i.e., the normal mode.
The jet-propulsion watercraft may further comprise: a target value table that prestores a target value for one of the cruising speed of the watercraft and the torque of the engine, and the target value according to the cruising speed or the engine torque may be read from the target value table, and the engine speed may be increased so that the cruising speed or the torque becomes the read target value. Thereby, the control for setting the target value can be simplified. To obtain the target value for the cruising speed or the torque that gives the rider preferable steering feeling, the engine speeds associated with a variety of cruising speeds or torques are experimentally increased.
The jet-propulsion watercraft may further comprises an engine speed sensor for detecting the engine speed to calculate the torque from the engine speed detected by the sensor (and/or throttle position). Likewise, the cruising speed can be calculated from the engine speed.
For the calculation of the torque from the engine speed, the obtaining means may comprise a torque conversion table that prestores the relationship between the engine speed and the torque, and the torque according to the detected engine speed may be read from the torque conversion table. The table may be replaced by an arithmetic expression of torque using the engine speed and the throttle position as parameters. It should be noted that the torque can be simply calculated only from the engine speed because the throttle position is substantially unnecessary at the throttle-close operation. Further, the crankshaft of the engine may be provided with a transducer for directly obtaining the torque. The same is the case with the cruising speed.
In the jet-propulsion watercraft, the obtaining means may comprise an offset table that prestores an offset value used for offsetting the torque stored in the torque conversion table according to acceleration of the engine; and an acceleration obtaining means for obtaining the acceleration of the engine, and the torque read from the torque conversion table may be offset according to the acceleration. Thereby, more accurate torque allowing for the inertia of the watercraft can be obtained.
In the jet-propulsion watercraft, the acceleration obtaining means may comprise an engine speed memory for sequentially storing the engine speed detected by the engine speed sensor; a calculating means for calculating a difference value between two engine speeds stored in the engine speed memory; a difference value memory for sequentially storing the difference value calculated by the calculating means; and a cumulating means for cumulating difference values stored in the difference value memory, and the acceleration of the engine may be calculated based on the cumulated value. In the engine speed memory, all of the engine speeds detected by the engine speed sensor in a predetermined time cycle may be stored or they may be partially stored. Further, the engine speed sensor may detect the engine speed for every control clock or partially detect the engine speed.
In the jet-propulsion watercraft, the engine may be adapted not to conduct combustion in part of or all of a plurality of cylinders of the engine for a predetermined time period, that is, to conduct xe2x80x9cpartial-combustionxe2x80x9d, in order to set the increasing speed of the engine speed smaller. Thereby, when the throttle is re-opened thereafter, the engine speed can be re-increased quickly. Also, the ignition timing and/or the injection timing in part of or all of the plurality of cylinders may be changed.
According to the present invention, there is further provided a jet-propulsion watercraft comprising: a water jet pump that pressurizes and accelerates sucked water and ejects the water from an outlet port provided behind the water jet pump to propel the watercraft as a reaction of the ejecting water; an engine for driving the water jet pump; a steering operation means that operates in association with a steering nozzle of the water jet pump; a steering position sensor for detecting a predetermined steering position of the steering operation means; a throttle-close operation sensor for detecting a throttle-close operation; an engine speed sensor for sequentially detecting the engine speed; and an electric control unit, wherein during the detection of the predetermined steering position by the steering position sensor and the detection of the throttle-close operation by the throttle-close operation sensor, the electric control unit is adapted to judge whether or not a value associated with the engine speed detected in a second period before a first period between the detection point of these operations and a point before a given period from the detection point is larger than a predetermined value, and to increase the engine speed while judging that the value is larger than the predetermined value.
According to the jet-propulsion watercraft of the present invention, the engine speed is increased to the predetermined engine speed while the watercraft is steered, this operation is detected by the steering position sensor, and while the throttle-close operation is detected by the throttle-close operation sensor. Therefore, the water sufficient to turn the watercraft is ejected from the water jet pump, and the steering capability can be maintained even when the throttle-close operation is performed. Also, since the value associated with the engine speeds in a predetermined period (second period) before the detection of the throttle-close operation and the steering operation is used in judgment as to whether or not to increase the engine speed, this value may be substituted for the cruising speed without being influenced by the throttle work. Further, since the engine speeds in the second period before the first period hardly include the engine speeds quickly decreased just after the throttle-close operation, that is, the value associated with the engine speeds in the second period can be used as a more accurate value in substitution for the cruising speed.
In the jet-propulsion watercraft, the value associated with the engine speed in the second period may comprise a statistical value of a plurality of engine speeds in the second period. Also, the value associated with the engine speed in the second period may comprise an average value of the engine speeds in the second period. In this case, the calculation process of the engine speeds is performed simply and in a short time.
It is preferable that in the jet-propulsion watercraft, the first period is approximately 0.5 second and the second period is approximately 3 to 5 seconds.
According to the present invention, there is still further provided a jet-propulsion watercraft comprising: a water jet pump that pressurizes and accelerates sucked water and ejects the water from an outlet port provided behind the water jet pump to propel the watercraft as a reaction of the ejecting water; an engine for driving the water jet pump; a steering operation means that operates in association with a steering nozzle of the water jet pump; a steering position sensor for detecting a predetermined steering position of the steering operation means; a throttle-close operation sensor for detecting a throttle-close operation; a cruising speed obtaining means for obtaining a cruising speed of the watercraft; and an electric control unit, wherein the electric control unit is adapted to increase the engine speed upon an elapse of a delay time according to the cruising speed obtained by the cruising speed obtaining means after the steering position sensor detects the predetermined steering position and the throttle-close operation sensor detects the throttle-close operation.
According to the jet-propulsion watercraft, the engine speed is increased while the watercraft is steered, this operation is detected by the steering position sensor, and while the throttle-close operation is detected by the throttle-close operation sensor. Therefore, the water sufficient to turn the watercraft is ejected from the water jet pump, and the steering capability can be maintained even when the throttle-close operation is performed. Also, since the timing of the start of increasing the engine speed is delayed according to the cruising speed obtained by the cruising speed obtaining means, the cruising speed decreases during the delay time even when the watercraft is cruising at a speed relatively larger than the upper limit to which engine speed is increased. Consequently, transition to the steering assist mode control can be improved.
The timing of the start of increasing the engine speed may be delayed proportional the cruising speed and a cruising speed sensor for detecting the cruising speed may be used as the cruising speed obtaining means. Also, the cruising speed may be calculated from the engine speed.
The jet-propulsion watercraft may further include a delay time table that prestores delay time according to the cruising speed, and the delay time according to the obtained cruising speed may be read from the delay time table and the timing of start of increasing the engine speed may be delayed by the read delay time. Thereby, the control for the delay in the start of increasing the engine speed can be simplified. The delay time according to the cruising speed can be obtained by actually measuring the times that give the rider preferable steering feeling.
The above and further objects and features of the invention will more fully be apparent from the following detailed description with accompanying drawings.